The invention relates to a motor that has a stator with different magnet poles and has a rotor with a matched number of permanent magnet poles, in which the air gap surfaces in the region between the stator and rotor are provided with fine gearings in order to reduce the torque between them.
A similar motor has been disclosed by U.S. Pat. No. 3,604,961. In this instance, the electrically excited rotor, which is embodied as an internal rotor, has a uniform, meander-shaped fine gearing teeth on its circumference so that it is designed to be radially symmetrical in this direction. The poles of the stator are embodied as permanent magnets, but are not disposed uniformly in the circumference direction since they alternatingly assume an angle of less than and greater than 360xc2x0/xc3xa7, wherein xc3xa7 represents the number of poles. The deviation angle is then selected so that a more uniform magnetic field distribution is produced in the circumference direction between the rotor and the stator. This leads to the reduction of the torque between the rotor and stator. Without this offset of the permanent magnets, the numbers of poles would cause a number of non symetrical to be produced between the rotor and stator, which could be detected when manually spinning the rotor and could result in an unsteady and noise-encumbered operation of the motor.
This known reduction of the torque, however, requires a complex design of the stator which depends on the precise installation of the permanent magnets. Furthermore, this design of the motor more or less limits the reduction of the torque.
An object of the invention is to produce a motor with compensation of the torque, which is simple in design and operationally reliable and which offers a significantly improved potential for reduction and compensation of the torque.
The offsetting of the fine gearing teeth in the vicinity of the air gap surfaces of the stator produces a symmetrically designed permanent magnet rotor which is simple to manufacture and produces definite magnetic field ratios in the circumference direction that can be influenced in a number of ways via the fine gearing teeth disposed on the stator. In this connection, the stator can still be designed as essentially symmetrical. The compensation of the torque remains limited to the design of the fine gearing, teeth which can be produced together with the formation of the magnet poles by means of a simple stamping of a xe2x80x9csolid armaturexe2x80x9d. Therefore other improvements of the torque compensation can also be easily incorporated into the manufacturing process of the motor since only the stamping procedure needs to be correspondingly modified. Moreover, a power supply by means of sliding contacts is no longer necessary since this can take place by means of a simple electronic control circuit.
A particularly simple design of the motor is produced by virtue of the fact that the number of magnet poles of the stator corresponds to the number of permanent magnet poles of the rotor, wherein the provision is made in particular that the stator is embodied as an internal stator and the rotor is embodied as an external rotor.
According to one embodiment, the effective compensation of the torque is produced by the fact that the offset of the fine gearing of the pole pairs identically and preferably corresponds to half a spacing of the fine gearing teeth.
With regard to the design of the rotor, according to one embodiment, the provision can be made that the permanent magnet poles of the rotor are constituted by means of individual permanent magnets that are distributed uniformly over the circumference of the rotor and that have a polarity that alternates in the circumference direction, wherein the individual permanent magnets can also be magnetized in a single-pole fashion.
Another embodiment for the rotor can be produced by the fact that the permanent magnet poles of the rotor are constituted by a number of two-pole annular segment permanent magnets distributed uniformly over the circumference of the rotor, which are disposed with their poles in the same direction toward the circumference, wherein the permanent magnet poles can also be constituted by multi-pole annular segment permanent magnets.
The fine gearings are embodied as meander-shaped in a known fashion, where in the simplest case, the teeth and the tooth spaces of the fine gearing teeth have identical widths and depths.
An extensive compensation of torque is produced by the fact that the teeth and the tooth spaces of the stator have different widths, but have identical depths and are supplementary to each other in the pole pairs, or by virtue of the fact that the widths of the teeth of the one pole and the tooth spaces of the other pole of the pole pairs of the stator change in the same manner, at least in a partial region of the circumference. The number of the teeth and tooth spaces of the stator preferably is an integral multiple of the number of pole pairs formed.
The pole pair formation and the compensation of the torque can be embodied so that the teeth of the pole pairs of the stator, which are constituted by respectively adjacent or diametrically opposed magnet poles, are respectively offset in relation to one another and on the other hand, can be embodied so that the teeth of pole pairs of the stator, which are constituted by magnet poles respectively offset by two pole spacings, are respectively offset from one another. In both instances, the teeth of the pole pairs are offset in antiphase in the circumference direction. In the event of a fixed or continuous eccentricity of the rotor, however, the effectiveness of the compensation is limited.
In higher-poled motors, it is more favorable to dispose the teeth in antiphase by a double pole line, as the second embodiment demonstrates.
The influence of the rotor eccentricity is canceled out in these motors.
For the effectiveness of the compensation of the torque, the advantageous provision should be made that the depth of the teeth and the tooth spaces should be greater than or equal to the air gap width between the stator and the rotor.
The invention will be explained in detail in conjunction with exemplary embodiments depicted in the drawings.